3D GPR Software

We use a Mala 3XM GPR to locate utilities in addition to our typical EM equipment. My employer has asked me to research 3D software for our GPR data for selling this service, and as an add-on service for our clients who want more then just paint on the ground and survey. I've looked around, and all I could find is this GPR Slice program, which is super expensive with annual fees. Were more interested in a one time buy. Does anyone know of, or use any programs like this?

Re: 3D GPR Software

Originally Posted by NoviceLiner

We use a Mala 3XM GPR to locate utilities in addition to our typical EM equipment. My employer has asked me to research 3D software for our GPR data for selling this service, and as an add-on service for our clients who want more then just paint on the ground and survey. I've looked around, and all I could find is this GPR Slice program, which is super expensive with annual fees. Were more interested in a one time buy. Does anyone know of, or use any programs like this?

Thanks,

Novice Liner

There are a few out there, including offerings from Mala for psuedo-3D rendering of subsurface targets. There are many other considerations to ponder as you consider moving ahead with this; 1) do you realize that what you are producing is a psuedo-3D image? 2) do you understand the amount of scanning time and number of profiles that will have to be collected in order to render the psuedo-3D image? 3) are you intending to declare a level of accuracy to your clients? if so, what are basing the accuracy on? 4) are you prepared to incorporate a GPS system into your X3M or are you intending to scan on a measured grid basis? 5) if you incorporate GPS, who will certify accuracy? Are you or someone in your firm a licensed surveyor?

Other than the Mala 3D Vision software, GPR Slice is the right choice for natively reading Mala's *.rd6 file formatsMala 3D Software

Re: 3D GPR Software

I'm also super interested in getting a GPR eventually. Great post GWJ. Sounds like you know your stuff. I'm guessing that the Mala 'easy locator' or whatever the model name is, is an entry level GPR unit that tends to be the least expensive solution out there at the moment?

Is it reasonable to expect the learning curve to GPR is harder than electromagnetic locating? Or easier? I'm sure you don't need a transmitter to hook up to something for it. Doesn't the software have to interpret the results of the scan which takes a long time? How long would it take to survey, say like 100 square feet with a mala GPR?

Re: 3D GPR Software

Thank you for your reply.

1) Pseudo-3D? I'm guessing that's not quite 3D. Just an interpretation?
2) I don't know how much scanning time and profiles it takes to achieve psuedo-3D.
3) I would like to give our clients accuracy, with mapping (I suppose GPS will help), and a marketing tool to show what could be found with GPR in addition to standard EM equipment. Yes, we have many licensed surveyors in our outfit.

Re: 3D GPR Software

Originally Posted by DigScout

I'm also super interested in getting a GPR eventually. Great post GWJ. Sounds like you know your stuff. I'm guessing that the Mala 'easy locator' or whatever the model name is, is an entry level GPR unit that tends to be the least expensive solution out there at the moment?

Is it reasonable to expect the learning curve to GPR is harder than electromagnetic locating? Or easier? I'm sure you don't need a transmitter to hook up to something for it. Doesn't the software have to interpret the results of the scan which takes a long time? How long would it take to survey, say like 100 square feet with a mala GPR?

Mala's Easy Locator is indeed an entry level machine, but nonetheless capable. You can enhance Easy Locator data if you purchase the upgraded EXM interface screen that will allow you to record your GPR data to a USB thumb drive for post-processing.

Scanning (not surveying, careful as "surveying" implies that you are recording information with a certified geospatial accuracy level) does not require any separate transmitter as the GPR system incorporates a transmitter and receiver into one unit. Electromagnetic Signal Pulses are emitted from the unit and return signals (bounced back) are received and displayed on the screen as a hyperbole (see image). They are highly interpretive and proficiency with GPR requires a good amount of theory knowledge and a ton of hands-on field experience.

Re: 3D GPR Software

Originally Posted by NoviceLiner

Thank you for your reply.

1) Pseudo-3D? I'm guessing that's not quite 3D. Just an interpretation?
2) I don't know how much scanning time and profiles it takes to achieve psuedo-3D.
3) I would like to give our clients accuracy, with mapping (I suppose GPS will help), and a marketing tool to show what could be found with GPR in addition to standard EM equipment. Yes, we have many licensed surveyors in our outfit.

Thank you GWS_CAS

Pseudo-3D is indeed an interpretation as the image is derived from multiple bi-directional scans performed in a measured or surveyed grid pattern. The software, with with substantial human interpretation, uses each hyperbole point as directed by the operator to indicate the top of target. These points are then strung together to create the target image with the gaps in between scan passes being interpolated by the software. The software draws in the target shape that was defined by the operator. So, if the operator says it is a 4" pipe, the software draws a cylindrical image at each of the chosen hyperboles and then creates an interpolated cylindrical image between those points. See image below and note that all "pipes" are the same diameter and color as these were defined by the software operator.

If you look at a GPR unit, Mala, Noggin, etc, you will note that the antenna casing is roughly 12" - 14" wide, but the actual antenna inside is a 4" wide (at its widest point) copper foil shaped like a bowtie. So, even though you think you are scanning an area as wide as the GPR unit itself, you are actually only scanning an area about 4" wide.

In order to get an accurate representation of the subsurface target, you will need to know what size it is reported to be or actually is. You can imagine if you were providing an image to a client, and you reported the target as 4" diameter and it is actually 16", then your accuracy is history and your client may have a bigger conflict than was anticipated based on your report and image.

In order to derive a true 3D image of a target, it must be scanned with multiple antennas simultaneously (an array), where each antenna "sees" the target at a slightly different intercept angle and "time" (nanoseconds). The true 3D configuration and image of the target can be depicted as follows:

Positional accuracy is of paramount importance. The desired level of positional accuracy can be accomplished with an interfaced GPS system where the radar system records a specific x, y & z coordinate for each recorded hyperbole in a single channel GPR system, or via a measured and surveyed grid (see image). Or, if you have multi-antenna systems like ours it can be continuously surveyed by a robotic total station.

Re: 3D GPR Software

Here are some actual 3D plots from a recent 3D Radar Tomography project we performed. We convert our 3D GPR imagery to point clouds for use in CAD software (Usually AutoCAD Civil 3D) where our 3D GPR data can be incorporated into the client's design files as our 3D GPR data is certified in accuracy to 0.083' horizontally (x, y axis) and 0.25' - 0.417' vertically (z axis) without exposure. With "ground truthing" or targeted soft digs for calibration we can improve our geospatial accuracy to less than 0.083' x, y and 0.1 - 0.25 z. We then certify (PSM Sign & Seal) our results.

Since we use a multi-channel arrayed GPR system (17 antennas) that pulse more than 10 times per lineal foot, and we survey continuously all movement of the system with a robotic total station, we derive a true 3D image.

Re: 3D GPR Software

Amazing posts GWJ_CAS. Truely great information about GPR that you are sharing with the rest of us EM guys. I agree with you on the point that field experience with a GPR is a must. Classroom training just isn't enough.

Just one last question for you. Would the GPR still be able to find plastic pipe that is completely plastic with absolutely no trace of any conductive material such as a tracer wire?

Re: 3D GPR Software

Originally Posted by DigScout

Amazing posts GWJ_CAS. Truely great information about GPR that you are sharing with the rest of us EM guys. I agree with you on the point that field experience with a GPR is a must. Classroom training just isn't enough.

Just one last question for you. Would the GPR still be able to find plastic pipe that is completely plastic with absolutely no trace of any conductive material such as a tracer wire?

Yes, GPR is the only way to accurately locate plastic / non-conductive (PVC, HDPE, PE, ACP, PCCP, VC, etc) facilities as it "compares" density differentials. The density of the buried facility is different from the soil in which it is buried. In rare cases, some plain concrete (non-reinforced), AC (Asbestos) and PCCP pipe can "blend" into its surrounding soil medium making it very difficult to discern the pipe itself, however, the open annulus of the pipe remains and appears as a void (density variation) which radar "sees". When using a 2D GPR system, "piecing" these voids together in the separate scans/profiles is the only way to locate the facility. When using our 3D RT system, such voids show up as a continuous image making the identification easier.

We have run into several places where the soil is so dense, particularly in very south Florida, where concrete and asbestos pipe are often "blended" with the surrounding soil medium and the identification of the void is the only way to "see" them. To give you an idea of what I mean, concrete has a typical measured density of 140 to 150 lbs per cubic foot and south Florida limestone has a density of 144 lbs per cubic foot, another soil variation called Miami Oolite has a density of 137 to 146 lbs per cf, so you can see how concrete and/or AC pipe can blend and virtually disappear in such soils making void identification the only way.